during observations if the floodlights and motors were operated for 

 many hours. 



INTERNAL LAY-OUT OF THE CABIN 



The cabin of the Trieste was laid out in much the same way as that 

 of the balloon FNRS and also of the FNRS 2. 



At the bottom of the cabin an aluminium ring of 47 in. diameter 

 served as a base. On this ring were six aluminium uprights of i • 1 8 in. 

 square section and 23-6 in. apart: they supported a second ring of the 

 same diameter as the first, which came quite close to the top of the 

 cabin. The whole formed a rigid cage. To hold this in place, the top 

 part had to be jammed against the top of the cabin. But an important 

 detail of construction enters into one's calculations at this point. 



If the cabin goes down to i\ miles, the external pressure causes all 

 its dimensions to decrease. The diameter decreases by 0-065 i^i. and the 

 two rings, which are 5 ft. 3 in. apart, would be brought closer by 

 0-0475 ii^-? if both were touching the cabin. Moreover, at the bottom of 

 the sea, the temperature of the body of the sphere will be lower than 

 when it was fitted up, while the temperature inside will not drop so 

 much. If, for example, the difference in temperature between the cabin 

 and the uprights were 45 °F., the uprights would be cramped to the 

 extent of 0-176 in. In short, the effect would be that the sphere forced 

 down the uprights 0-065 i^^- The consequence of this would not be that 

 they broke, but they would buckle or bend sideways. It is quite simple 

 to calculate how much they would bend ; the lateral deflection, in fact, 

 would amount to i-i in. halfway up the uprights. To avoid this, I put 

 strong steel springs in a housing bored in the upper part of each 

 upright, to force pieces of metal against the cabin with a force of 1 10 lb. 

 for each upright. Strips of rubber placed between these pieces of metal 

 and the cabin, as well as a rubber ring lodged between the lower ring 

 and the base of the cabin, produced such friction that the whole centre 

 cage, while remaining free to expand or contract, was nevertheless held 

 rigid. 



On the lower ring a piece of sheet aluminium formed the floor. 

 The free space between this floor and the spherical bottom of the cabin 

 was 7-87 in. high at the centre : we called it the cellar. A trapdoor gave 

 access to it. This space was not wasted, as we used it to store the reserve 

 containers of alkali and the bottles of compressed air, which were 

 needed to empty the entrance shaft after each dive. The observer 



[ 102 ] 



